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North Vancouver, Canada

Dowling C.A.,BGC Engineering Inc. | Santi P.M.,Colorado School of Mines
Natural Hazards | Year: 2014

Debris flows cause significant damage and fatalities throughout the world. This study addresses the overall impacts of debris flows on a global scale from 1950 to 2011. Two hundred and thirteen events with 77,779 fatalities have been recorded from academic publications, newspapers, and personal correspondence. Spatial, temporal, and physical characteristics have been documented and evaluated. In addition, multiple socioeconomic indicators have been reviewed and statistically analyzed to evaluate whether vulnerable populations are disproportionately affected by debris flows. This research provides evidence that higher levels of fatalities tend to occur in developing countries, characterized by significant poverty, more corrupt governments, and weaker healthcare systems. The median number of fatalities per recorded deadly debris flow in developing countries is 23, while in advanced countries, this value is only 6 fatalities per flow. The analysis also indicates that the most common trigger for fatal events is extreme precipitation, particularly in the form of large seasonal storms such as cyclones and monsoon storms. Rainfall caused or triggered 143 of the 213 fatal debris flows within the database. However, it is the more uncommon and catastrophic triggers, such as earthquakes and landslide dam bursts, that tend to create debris flows with the highest number of fatalities. These events have a median fatality count >500, while rainfall-induced debris flows have a median fatality rate of only 9 per event. © 2013 Springer Science+Business Media Dordrecht. Source

Bommer C.,WSL Institute for Snow and Avalanche Research SLF | Phillips M.,WSL Institute for Snow and Avalanche Research SLF | Arenson L.U.,BGC Engineering Inc.
Permafrost and Periglacial Processes | Year: 2010

Mountain infrastructure can be negatively affected by ground-ice degradation induced by the combined effects of construction activity, the structure itself and climate change. Modification of subsurface conditions may cause differential settlement, creep and deformation of structures, substantially shortening their service life. Permafrost detection techniques and adaptive design methods taking into account changes in the geotechnical properties of the ground are rarely applied on construction sites in the Alps. The analysis of potential structural sensitivities to changes in the substrate and the determination of failure consequences are necessary for the successful design of durable infrastructure. Appropriate monitoring systems allow timely diagnoses and the application of suitable remedial measures. The use of specially conceived technical solutions in mountain permafrost is becoming widespread, yet there is not a commonly accepted state-of-the-art. New recommendations provide an overview of practical solutions for the construction and maintenance of durable infrastructure in mountain permafrost. © 2010 John Wiley & Sons, Ltd. Source

Jakob M.,BGC Engineering Inc. | Friele P.,Cordilleran Geoscience
Geomorphology | Year: 2010

Natural hazard and risk assessments are predicated on a detailed understanding of the relationship between frequency and magnitude of the hazardous process under investigation. When information is sought from the deep past (i.e., several thousand years), continuous event records do not exist and the researcher has to rely on proxy data to develop the frequency-magnitude (F-M) model. Such work is often prohibitively expensive and few well-researched examples for mass movement are available worldwide. The Cheekye fan is a desirable location for land development and has a depth and breadth of previous research unprecedented on any debris-flow fan in Canada. We pursued two principal strains of research to formulate a reliable F-M relationship. The first focuses on stratigraphic analyses combined with radiometric dating and dendrochronology to reconstruct a comprehensive picture of Holocene debris-flow activity. The second approach examines hydrological limitations of rock avalanche evolution into debris flows through either entrainment of saturated sediments or by failure of a landslide-generated dam and upstream impoundment. We thus hypothesize that debris flows from Cheekye River can be separated into two quasi-homogenous populations: those that are typically triggered by relatively small debris avalanches, slumps, or rock falls or simply by progressive bulking of in-stream erodible sediments; and those that are thought to result from transformation of rock avalanches. Our work suggests that debris flows exceeding some 3 million m3 in volume are unlikely to reach the Cheekye fan as a result of limited water available to fully fluidize a rock avalanche. This analysis has also demonstrated that in order to arrive at reasonable estimates for the frequency and magnitude of debris flows on a complex alluvial fan significant multidisciplinary efforts are required. Without the significant precursor investigations and the additional efforts of this study, life and property may be jeopardized or the design of debris-flow mitigation may be subject to considerable and unquantifiable error. © 2009 Elsevier B.V. All rights reserved. Source

Quinn P.E.,BGC Engineering Inc. | Diederichs M.S.,Queens University | Rowe R.K.,Queens University | Hutchinson D.J.,Queens University
Canadian Geotechnical Journal | Year: 2011

A new model is proposed for the development of large landslides in sensitive clay, and supported by concepts from fracture mechanics. A key assumption in this new model is that the complete failure surface develops before the onset of significant movement, thus predetermining the final extent of failure. The appearance of retrogression is actually the rearward advancing disruption of a monolithic slide mass over a growing zone of liquefied clay. It is seen that the likelihood of propagation of failure, and the resulting occurrence of a large landslide, depend primarily on the brittleness of the sensitive clay. The potential length of shear band propagation is limited by slope geometry, and increases for higher riverbanks and for flatter slopes above the riverbank. The model explains why large landslides in sensitive clay often terminate just adjacent to a reverse break in slope, such as an older landslide crater or a stream gully. The model also indicates that large landslides in sensitive clay could be expected to occur suddenly after a large single perturbation, such as an earthquake, or after a seemingly innocuous small trigger following the accumulation of a large number of annual load cycles, as observed frequently in nature. Source

Quinn P.E.,BGC Engineering Inc.
Canadian Geotechnical Journal | Year: 2013

This paper describes geostatistical analyses completed at a discontinuous permafrost site in central Yukon to develop a predictive model for the presence of late-season frozen ground in support of planning and design for potential site development. The most important factors in the bivariate statistical model were soil type, as determined through terrain analysis, and slope aspect, as inferred from available topographic data. The other three factors included in the final model were profile curvature, slope angle, and ground elevation, each interpreted from available topographic data. The resulting model subdivides the site into three broad classes of frozen ground likelihood: low, where frozen ground can be expected to be encountered in late summer at 15% of observation locations; medium, where 50% of the ground is expected to remain frozen; and high, where 85% of the ground is expected to remain frozen. New test pit and borehole data from the summer of 2012 were used to verify model performance. The inferred correlations between frozen ground and soil type, aspect, curvature, slope, and elevation obtained in this case study may provide useful information relative to expected permafrost occurrence at sites in central Yukon with similar geology and physiography. Source

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